ISBN 9783843928304

978-3-8439-2830-4, Reihe Physik

Hendrik Niederbracht
Process approaches for on-chip excitation and enhancing the optical collection efficiency of quantum dot based single-photon emitters

167 Seiten, Dissertation Universität Stuttgart (2015), Softcover, A5

Zusammenfassung / Abstract

In the present thesis, processes to efficiently generate and collect single photons from semiconducor quantum dots (QDs) are developed. This implies on the one hand the quasi-resonant on-chip excitation of the QD and on the other hand an enhanced optical collection efficiency. For the latter, two approaches are pursued, one is the creation of a thin-film structure combined with a metal mirror and a solid immersion lens (SIL) and the other, the direct fabrication of micro lenses into the semiconductor material.

For the thin-film approach the AlGaInP material system was used. Thus, a reliable semiconductor process has to be developed to produce a membrane structure below 100 nm thickness containing optically active InP QDs with a low density. The fabrication process development is discussed in detail. The optical characteristics of the QDs in this thin membrane are then compared to the optical characteristics of QDs in an unprocessed sample. This membrane structure is then combined with a SIL to enhance the optical collection efficiency. Within this thesis a Zirconium dioxid SIL was utilized to enhance the collection efficiency of the QDs.

Another possibility to enhance the collection efficiency is the monolithic integration of a SIL into a QD sample structure. This idea was followed in the GaAs semiconductor system with InGaAs as QD material. By using a FIB, hemispheres in the micrometer regime were successfully processed in the top layer of the sample. The optical collection efficiency is then studied and compared with simulations.

For the quasi-resonant excitation of the QDs a completely dry-etched ridge laser structure on InP QD-containing semiconductor structure is developed. The major point in the fabrication of these ridge lasers for on-chip integration is the fabrication of very good facets using dry etching techniques. This developed process will be discussed in detail. The successful fabricated ridge laser are characterized by studying the emission properties at room temperature and cryogenic temperatures.